Rubella virus contains single-stranded RNA as a genome and replicates in the cytoplasm of infected cells. Rubella virus has been grouped with the togaviruses and the paramyxoviruses, yet it does not fit in either class. The overall objective of this research project is characterize the rubella virus antigens in respect to structure and synthesis and to determine which antigen elicits neutralizing antibody. The answer to these should provide insight into the classification of rubella virus since the togaviruses appear to use post-translational cleavage of precursor molecules as a mechanism of viral protein synthesis. Although the rubella virus RNA has been reported to be messenger RNA, no evidence has been obtained that a precursor protein molecule is present in infected cells. The acrylamide gel profiles of the rubella proteins is more similar to that of the paramyxoviruses than that of the togaviruses. Initially, efforts will be aimed at selecting the most advantageous system for production of rubella virus. Purified rubella virus will then be disrupted into it component antigens, and each will b subjected to chemical and physical characterization to determine polypeptide chain composition. Each purified antigen will be injected into rabbits and the subsequent antibody response will be assayed for antibody function.